Breathing is part and parcel of the human condition. If you don’t breathe, you can’t really do much. The air around us, however, is not exactly as pure as it once was. Arguably, the air around us was never really that pure in the first place, but that’s delving a little too deep. In past ages, people sometimes feared drinking water during times of war because there was a very good chance it was poisoned by the enemy. An underhanded tactic, to be sure, but one that was used nonetheless. In the modern world, people may not be as paranoid about the air they breathe, but there is no denying that things like second-hand smoke and the possibility of airborne bacterial infection make breathing a hazardous thing.
You’ve probably heard a horror story or two about the potential side effects of breathing in second-hand smoke. You’ve probably been told that, since there’s no filter to reduce the amount of toxins and carcinogens, you’re at greater risk than smokers if you allow yourself to be exposed regularly. Smokers have the filters on their cigars and cigarettes to reduce the damage, but people who stand there and take in the second-hand...